Conventionally, as a technique for the case in which the power to be transmitted in power transmission by radio is small, there has been a technique referred to as so-called “passive RFID” in which, by using the radiation field of electromagnetic waves radiated from a transmitter, a receiver captures the electromagnetic field, converts it to alternating current, and rectifies the current, so that the power that can be used as a power supply is obtained (for example, see Non-Patent Document 1).    Non-Patent Document 1: RFID Handbook Second Edition (written by Klaus Finkenzellar, translated by Software Engineering Institute, published by The Nikkan Kogyo Shimbun, Ltd., May 2004)